A zone cooling system was tested to modify the greenhouse microclimate for plant growing with the minimum energy input during hot weather. The cooling system was equipped with perforated polyethylene tubes to distribute cool air from spot coolers into the zone in which spinach plants were grown in pots in a plastic greenhouse during the summer of 1991. The ratio of the cooling capacity of the spot coolers to the floor area of the cooled zone in the greenhouse was 0.18 kW⋅ m^-2. The cooling system was turned on when one of the air temperature sensors at four positions in the plant zone exceeded 30°C and turned off when all the air temperature data at these positions decreased to 27°C. The overall transmissivity of greenhouse cover and shading materials to solar radiation was 0.54. Watering was done to meet the requirements of the spinach plants. The microclimate conditions in the cooled zone were compared with that in a naturally ventilated zone in a similar greenhouse.
During sunny days throughout the experimental period when the daily solar radiation exceeded 18 M J⋅m^-2⋅day^-1, we were able to maintain the daily maximum air temperature in the plant zone from 30.4 to 36.8°C compared to from 32.0 to 39.0°C in the naturally ventilated plant zone. During the above experimental days, the electrical energy required to run the system was 0.57 to 0.68 M J⋅m^-2⋅day^-1, and the daily total cooling time was 8.2 to 9.5 hr⋅day^-1. Under these conditions, the daily degree-hour value in the cooled plant zone was 22 to 2 7°C⋅hr⋅day^-1 lower than that in the naturally ventilated plant zone. The growth of spinach plants in both cooled and naturally ventilated zones showed that the fresh weight of the top part of the spinach plants in the cooled zone exceeded twice that of the naturally ventilated environment on the 45th day after sowing.

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Effects of temperature and interval of watering time on the yield and the morphological characteristics of fruit-bodies of shiitake mushroom (Lentinus edodes) was studied with sawdust-culture method. Four treatments including two different temperatures (15°C constant and 23°C (0600-1800 hr) /15°C (1800-0600 hr) ) and two different intervals of watering time (every 24 and 48 hr) were applied to two different commercial sawdust-cultured shiitake mushrooms.
When the medium was watered every 24 h, fresh yield of fruit-bodies was 1.3 times as much as that watered every 48 h. In addition, the fruit-bodies could be harvested earlier, the fresh weight per fruit-body and its water content was higher, its size was larger and its cap was thinner than those watered every 48 h.
When the temperature was 23/15°C, the fresh weight per fruit-body and the number of harvested fruit-bodies tended to be larger than those at the temperature of 15°C constant. The start time of harvest was 5-10 days earlier than that at 15°C. The length of the stipe was longer and the cap was thinner than those at 15°C.
It was obvious that the temperature and the interval of watering time affected the yield and the shape of the fruit-body of shiitake mushrooms using sawdust-culture method.

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Bud formation of Spiraea cantoniensis Lour.‘Mizuho’ grown at 15°, 20°, 25°C and natural temperature was investigated from the morphological point of view.
1. Spring shoots grew faster with increasing temperatures, but the shoot elongation stopped early at 20°and 25°C.
2. Number of scales of vegetative axillary bud of the spring shoot increased with increasing temperatures. Number of inner bracts (transition leaves) of the bud was approximately same in all treatments. Number of leaf primordia of the bud was the greatest at 20°C and the least at 25°C.
3. Number of leaf primordia of developed vegetative bud, except those at constant 15°C, increased few from November 1 through February 1 at constant temperatures and also under winter low temperatures.
4. At constant 15°C, inflorescences were begun to initiate five months after the start of treatment and their florets developed normally. At 20°C, inflorescences initiated two months later than those at 15°C, but all of them were abnormal ones forming bracteoles exclusively and eventually aborted at the bracteole-stage of development. No inflorescence was formed at 25°C.
5. When the plants under each temperature were transferred to outdoors on November 1 and returned to the initial temperature on February 1, most flower buds came into bloom at 15°C and 20°C, and also partially at 25°C.

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The activities of F. oxysporum f. sp. cucumerinum related with living roots of plants cultivated in the soil were discussed.
Number of the pathogens colonized on soybean roots was the most, then decreased in the order of cucumber and sorghum, there were no clear differences between young roots and adult ones when the plants were cultivated in the continuous cropping fields infested with the pathogen. Also, the pathogen infested in cucumber roots, and became more and more with the passage of cultivated time in the field, but almost not in soybean and sorghum roots. More pathogens attacked the tissues near apexes of root and less to the base. However, they did attacked all parts of the root when their population reached 10⁴ in 1 g soil. There were many soil fungi colonized on tips also, and a few invaded into root tissues. The number of colonized fungi decreased as the population of cucumber wilt pathogens increased in the soil.
The soil fungi were divided into 3 groups according to the colonization sites on root, but fungi showing antagonistic activity to cucumber wilt pathogen were recognized in all 3 groups. Inhibited force of a fungus to wilt pathogen in the soil correlated with its colonizing ability to cucumber roots other than with the antagonism on the medium. However, the suppression to cucumber wilt disease as demonstrated in sterilized soil were lost or reduced in the natural soil.

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Cool season vegetables such as carrot, garland chrysanthemum, komatsuna, pea, Japanese radish, radish, spinach, turnip and Welsh onion were grown in hydroponics for 4 weeks. The solution temperatures of the three plots were regulated and the solution temperature of one plot was not regulated so as to maintain the solution temperatures to about 15°, 20°, 25° and 30°C. The effects of solution temperatures on root and shoot growth were investigated.
1. The optimum solution temperatures for root elongation varied in plant kinds used. The temperatures at the end of experiment were from 13° to 25°C. The optimum temperatures for spinach (13.3°C) and pea (13.7°C) were the lowest and those for Japanese radish (18.1°C), carrot (19.3°C), komatsuna (19.9°C), Welsh onion (19.9°C), radish (20.2°C) and turnip (20.2°C) were moderate high, and for garland chrysanthemum (24.7°C) was the highest.
2. When root elongation was measured weekly, the optimum temperatures for root elongation in some vegetables had a tendency to decline a little as they grew. Those kinds of plants were spinach, pea, Japanese radish, carrot, Welsh onion, radish and turnip.
3. Estimated optimum temperatures for root elongation calculated from the correlation between the mean solution temperatures and maximum root length varied also in plant kinds used. The values for pea and spinach were the lowest and those for radish, Welsh onion, garland chrysanthemum, komatsuna, Japanese radish and turnip were moderate high, and for carrot was the highest.
4. Increase of root dry weight was also affected by the solution temperatures. The optimum temperatures for root growth at the end of experiment used were from about 13° to 25°C. The values for spinach and pea were the lowest and those for komatsuna, Welsh onion, garland chrysanthemum, radish, turnip and carrot were moderate high, and for Japanese radish was the highest.
5. There was a significant correlation between leaf area and root growth; root fresh weight and maximum root length.

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A fact data base (FDB) was introduced to construct a new expert system to support tomato cultivation by using an AI-computer. In this expert system, inference for cultivation management of tomato plants can be optimized by interactions between forward inference and backward inference.
When a user of this expert system asked an arbitrary question concerning tomato cultivation, an inference engine of the computer began to acquire data related to the question from FDB. First, the computer conducted the forward inference, and the obtained result could be stored temporarily in the meta-working area of the computer memory. Furthermore, results obtained from the forward inference were used for backward inference, and inference could be optimized for the question.
In order to test this new expert system, FDB's for physiological data for tomato plants and climatic conditions for various cultivation locations were constructed in the computer memory and 836 rules for inference were set in the inference engine. When optimal times for seeding and transplanting for tomato plants were estimated for 41 different locations in Japan by using this expert system, time inferred by the computer was similar to that practiced actually in the locations, indicating that this expert system can be used for optimization of cultivation management.
Although a few deviations were observed, such deviation could be corrected readily, because FDB could be expanded easily. Thus, a new expert system developed here by using FDB may be used for other crops, if sufficient FDB and rules for inference are set appropriately.

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